Retarders (available in varying strengths) are applied to the mould face forming the surface requiring aggregate exposure. Extreme care must be taken to ensure an even coating of retarder is applied. The following day the surfaces are brushed & high pressure water blasted to remove the cement matrix & expose the aggregate. Care is needed to match the retarder strength to the aggregate size in the concrete mix.
This finish is usually used when the aggregate is required as the dominant feature or as a contrasting feature in conjunction with other finishes. Care should be taken in choosing its location as the finish is quite abrasive on contact. Repairs are usually unnoticeable.